To demonstrate the association between pre-pregnancy maternal overweight, obesity, and perinatal outcomes of singletons conceived by assisted reproductive technology (ART). Retrospective cohort study from 2006 to 2015 data from a single ART center. Assisted Reproduction Center, Northwest Women's and Children's Hospital, Xi'an, Northwestern China. We included 7,818 women undergoing ART and their singleton infants. None. The primary outcome measures were preterm birth (PTB), macrosomia, low birth weight, small for gestational age, and large for gestational age (LGA). We experienced an increase in the risk of PTB, macrosomia, and LGA in overweight and obese groups compared with that in normal-weight groups [PTB: overweight vs. normal weight: odds ratio [OR] = 1.44, 95% CI: 1.18-1.75; obesity vs. normal weight: OR = 1.53, 95% CI: 1.04-2.25; macrosomia: overweight vs. normal weight: OR = 1.78, 95% CI: 1.48-2.14; obesity vs. normal weight: OR = 2.16, 95% CI: 1.52-3.06; LGA: overweight vs. normal weight: OR = 1.63, 95% CI: 1.39-1.90; obesity vs. normal weight: OR = 2.11, 95% CI: 1.57-2.83]. We observed a significant interaction between maternal BMI and fresh/frozen embryo transfer on PTB and LGA ( = 0.030; = 0.030). Fresh embryo transfer significantly increased the effect of maternal BMI on LGA (fresh: OR = 1.14, 95% CI: 1.10-1.18; frozen: OR = 1.09, 95% CI: 1.04-1.13), and frozen embryo transfer increased the effect of maternal BMI on PTB (fresh: OR = 1.03, 95% CI: 0.99-1.08; frozen: OR = 1.09, 95% CI: 1.04-1.15). Pre-pregnancy maternal overweight and obesity were associated with higher risks of PTB, macrosomia, and LGA in ART-conceived singletons. These associations were affected by the timing of embryo transfer (fresh/frozen embryo transfer). Therefore, we recommend women before ART to maintain a normal BMI for the prevention of adverse perinatal outcomes.